1. Field of the Invention
The present invention relates to an improved fluid connector. More specifically, the invention relates to a molded or cast short radius return bend for use on horizontal shell and tube heat exchangers.
2. Related Art
U.S. Pat. No. 3,635,040 shows a shell and tube water chiller using a compartmentalized chamber at each end of a vessel with suitable partitions or baffles to direct the water flow through the tubes sequentially in series to achieve the desired cooling. The water chiller shown in U.S. Pat. No. 3,635,040 includes a heavy duty hinged stainless steel door for closing off the compartments at each end of the vessel during operation, and for allowing access for inspection and cleaning as required.
In order to maximize the cooling capacity of water chillers such as that shown in U.S. Pat. No. 3,635,040, it is desirable to maximize the water flow rate through the tubes of the water chiller. A large amount of pumping horse power is consumed by the prior art chillers in order to overcome the resistance to fluid flow occurring at each end compartment of the chiller as flow is directed from tube to tube in sequence by each rectangular end compartment.
The provision of stainless steel doors at each end of the vessel shown in U.S. Pat. No. 3,635,040 increases the complexity of fabrication of the vessel as well as its overall size. The compartmentalized chambers at each end of the prior art vessel for directing water flow through the tubes sequentially in series allows for spacing of 3 inch diameter tubes at approximately 4 inches from centerline-to-centerline, thereby allowing for a relatively compact vessel. However, an inherent disadvantage of using such compartments for directing flow from one tube to another is the relatively large pressure drop that occurs through the compartments.
The resistance to flow in a piping system is similar to the resistance of an object immersed in a flow stream and is made up of pressure (inertia) or shape drag and skin-friction (viscous) drag. For piping components such as bends and elbows, pressure drag is predominant. For bends and elbows, the loss is made up of pressure drag due to the change of direction of the flow and the creation of secondary flows in the component. One parameter used to describe the resistance to flow for piping components is the equivalent length of pipe expressed in terms of pipe diameters needed downstream of the component to dissipate the secondary flows generated by the components. A smooth surface in a flow component generates fewer secondary flows as fluids pass through the component than a surface with sharp transitions. As a result, a U-shaped flow component will have a smaller "equivalent length" than a rectangular-shaped flow component and will cause less of a pressure drop in fluid passing through the component. The power consumed by a pump in order to maintain a desired flow rate through a piping system increases in proportion to the pressure drop through the piping system. Therefore, the use of piping components with smaller "equivalent lengths" minimizes the required pumping horse power and energy consumption for the piping system.
Existing standard stainless steel U-bends for 3 inch tubes in a typical water chiller such as shown in U.S. Pat. No. 3,635,040, require a centerline-to-centerline distance of 9 inches. Increasing the centerline-to-centerline distance to 9 inches from the 4 inch distance in U.S. Pat. No. 3,635,040 would require the shell diameter of the vessel to be increased from 26 inches to 36 inches to accommodate the same number of tubes on 9 inch centerline-to-centerline, which would greatly increase the size, weight, shell thickness and cost of the vessel.
In addition, since the U-bend must be removable for sanitation inspection as required by the U.S.D.A. when the heat exchanger is used for food processing, the design must allow use of clamps or some other means to accommodate U-bend removal. No existing clamps on the market today are adapted for such close centerline-to-centerline designs.
Attempts to fabricate close centerline U-bends by fabricating square U-bends utilizing 45.degree. miter joints and 3 inch stainless steel pipes have the inherent disadvantage in that the U-bends cannot be ground and polished inside after welding and do not meet U.S.D.A. sanitation standards. The square corners within such fabricated fittings also result in a greater pressure drop through the fitting than produced in a fitting having a smooth U-shape configuration.